Fuel Reactivity Controlled Compression Ignition Research Articles

Experimental investigation on effects of ethanol fumigation in dual fuel reactivity controlled compression ignition engine

In recent years, in order to face the challenge provided by the more strict emission rules, a vast number of researchers have researched the notion of low temperature combustion, commonly known as LTC. Because LTC may simultaneously lower the emissions of NOx and PM from internal combustion engines, the theory of LTC has gained a lot of attention from people all around the world. RCCI is a promising combustion approach that can replace up to 80% of the total fuel energy with hydrous ethanol, resulting in good thermal efficiency as well as minimal emissions of NOx and soot from the engine. In recent years, a vast number of research have focussed on studying a variety of techniques to optimize the combustion process, as well as performance and emissions. The usage of hydrous ethanol engines with a high water content has the potential to considerably enhance the amount of energy utilized throughout the course of bio ethanol's life cycle as well as its CO2 emissions.We employed a Reactivity Controlled Compression Ignition (RCCI) engine in our project. We did this by applying the approach of low temperature combustion in order to cut down on the amount of soot that was produced as well as the levels of emissions such as NOx, PM, and CO emissions, etc. We put 100% DIESEL, 90% Diesel with 10% Ethanol, 80% Diesel with 20% Ethanol, 70% Diesel with 30% Ethanol, and 70% Diesel with 30% Hydrous Ethanol through their paces in a variety of loads ranging from 0 to 100, as well as 25, 50, and 100 cycles each. As a result of our study and observations, we have come to the conclusion that the combination of HYDROUS ETHANOL (30% Energy Fraction) and DIESEL (70%Energy Fraction) produces the best results when compared to other combinations of fuels. As a result, this combination results in a reduction in the creation of soot and also results in a reduction in the emission of NOx, CO, and PM. The RCCI engine utilizes this particular blend of fuel because it generates superior outcomes.

Cylinder Pressure Feedback Control for Ideal Thermodynamic Cycle Tracking: Towards Self-learning Engines

To meet increasingly strict future greenhouse gas and pollutant emission targets, development time and costs of heavy-duty internal combustion engines will reach unacceptable levels. This is mainly due to increased system complexity and need to guarantee robust performance under a wide range of real-world conditions. Cylinder Pressure Based Control is a major contributor to achieve these goals in advanced, highly-efficient engine concepts. Current Cylinder Pressure Based Control approaches use combustion and air-path parameters as feedback signals. These signals are not directly linked to engine efficiency; therefore, compensation for changing ambient conditions, engine ageing or differences in fuel qualities is a non-trivial problem. Contrary to other methods, the method presented in this paper aims to realise an idealised thermodynamic cycle by directly control of the entire cylinder pressure curve. From measured in-cylinder pressure, a new set of feedback signals is derived using principle component decomposition. With these signals, optimal fuel path settings are determined. The potential of this method is demonstrated for a dual fuel Reactivity Controlled Compression Ignition (RCCI) engine, which combines very high efficiency and ultra low nitrogen oxides and particle matter emission. For the studied RCCI engine, it is shown that the newly proposed optimisation method gave the same optimal fuel path settings as existing methods. This is an important step towards self-learning engines.

Effect of pilot injection strategy on the methanol-mineral diesel fueled reactivity controlled compression ignition combustion engine

Amongst all low-temperature combustion (LTC) strategies, reactivity-controlled compression ignition (RCCI) combustion garners more debate from researchers because of its excellent combustion and performance characteristics and lower emissions over a wide operating range. In this experimental investigation, the consequences of the start of diesel injection (SoIdiesel) timing using different pilot injection techniques, such as single and double pilot injection (SPI and DPI, respectively), have been investigated. Tests were performed at a fixed engine speed and load (1500 rpm and 3 bar BMEP, respectively) using different premixed ratios (rp: 0, 0.25, 0.50, and 0.75) of methanol on an energy basis. Experimental results indicated that the start of combustion (SoC) and combustion phasing (CP) advanced with advancing SoIdiesel. However, too advanced and retarded SoIdiesel timings resulted in combustion noise and misfire. The use of pilot injection was found suitable for the RCCI mode, especially at lower rp. However, SPI and DPI strategies didn’t show significant variations in the combustion characteristics. Exhaust gas temperature (EGT) showed a random trend with SoIdiesel timing, and it decreased with the increasing number of pilot injections. RCCI mode produced higher hydrocarbon (HC) and carbon monoxide (CO) and lower oxides of nitrogen (NOx) emissions. All these gaseous emissions decreased with advancing the SoIdiesel. Particulate matter (PM) analysis showed that the RCCI mode emitted relatively lower PM than the baseline CI mode, further reducing with increased methanol fuelling. PM emissions also decreased by retarding SoIdiesel, in which reduction in smaller particles was dominant. The analysis of critical parameters such as brake thermal efficiency (BTE), HC, NOx, and PM emissions suggested that the optimum rp of methanol and suitable injection strategy can significantly improve the combustion, performance, and emissions characteristics of the RCCI mode.

A comparative study on gasoline/diesel-fueled RCCI combustion at different premixed ratios and high-EGR diesel CI combustion in an IC engine under low load conditions

Low temperature combustion concepts in internal combustion engines have arisen as one of the solutions that reduce NOx and particulate emissions without a fuel consumption penalty. Among the combustion concepts, reactivity controlled compression ignition (RCCI) has the potential of being able to be achieved in a wider operating range than other low temperature concepts. On the other hand, exhaust gas recirculation (EGR) use in diesel-compression ignition (CI) engines is an effective way to reduce NOx emission. This study experimentally investigated the high-EGR CI fueled with diesel and gasoline/diesel fueled RCCI combustion modes in terms of combustion, performance, and emission at fixed energy inputs corresponding to low load conditions for different engine speeds. In RCCI combustion mode, different premixed ratios were also tested to determine their effects. The results show that CA50 locations in all high-EGR CI combustion occurred later than those of RCCI modes, which led to late peak pressure occurrence. By considering heat release rate curve characteristics, the controlled combustion phase emerged at the highest premixed ratio in RCCI as in the high-EGR CI combustion. RCCI combustion showed an improvement in smoke emissions, and the maximum improvement was attained by about 86%. In RCCI combustion, nitrogen oxide (NO) emissions at 2000 rpm engine speeds are significantly lower than that in high-EGR CI whereas the increasing premixed ratio at 1500 and 1750 rpm led NO emission to increase. Besides, RCCI combustion with the highest premixed ratios resulted in slightly higher brake thermal efficiencies (BTE). The maximum difference in BTE values was obtained by about 3.0% in favor of RCCI combustion.

Fuel reactivity controlled compression ignition engine and potential strategies to extend the engine operating range: A comprehensive review

• Key features exploration for future act PCCI/RCCI/DDFS engine. • We research the issues and challenges in medium and high engine load operating range. • The impact of direct dual fuel stratification techniques on combustion stability is evaluated. • A review of the oxidation mechanism of both high and low reactive fuels have achieved. • Successful implementation of duel fuels potentially leads to tuning charge stratification. • Engine phasing achieved by DDFS with direct injections of high and low reactivity fuel. The objective of this study is to explore various strategies i.e. reactivity stratification, thermal stratification, injection timing, and exhaust gas recirculation as key factors for prolonging the PCCI/RCCI/DDFS engine operational spectrum and suppressing the ringing intensity. Since most of the current motivating strategies can be lumped into the category of premixed Low-Temperature-Combustion (LTC), the potential of this paper is to demonstrate the robustness of LTC in addressing several challenges related to premixed charge compression ignition engine, viz., lack of phasing regulation of combustion at heavy engine loads and excessive pressure rises. With a premixed preparation strategy, however, emission species are seen to decrease, yet the challenges of pre-combustion charge preparation are present. This can deduct a noticeable extent of fuel energy. To avoid the steep trend of pressure rise problem that restricts LTC engines with their operating range, higher levels of fuel blending and regulating the timing of auto-ignition are used. This review demonstrates the ongoing progress in premixed LTC techniques aim to control of nitrogen oxides (NO x ), reduction of particulate matter (PM), and hydrocarbon (HC). In comparison to normal LTC operation, the duel fuel charge stratification might increase indicated thermal efficiency (ITE) by 5% to 7% across the survey. For various charge compositions, tests were made in homogeneous charge compression ignition (HCCI) and reactivity controlled compression ignition (RCCI). These results are provided and analyzed in comprehensive detail, with extensive correlations to model predictions and a thorough kinetic analysis. Furthermore, injection strategies were reviewed to accomplish highly efficient preparation of the combustion charge, reduce the combustion environment temperature, and enhance premixing. By highlighting relevant components of this rich and quickly growing field of knowledge, this study aims to give an insight to and summary of current studies on LTC combustion. As a result, this document serves as a fundamental collection of information and recommendations on the current state of combustion research on various fuels.

Statistical analysis on the effect of premixed ratio, EGR, and diesel fuel injection parameters on the performance and emissions of a NG/Diesel RCCI engine using a DOE method

In reactivity-controlled compression ignition (RCCI) engines, the ignition and combustion of premixed low reactive fuel (LRF) such as natural gas (NG) is controlled by the injection of high reactive fuel (HRF) such as diesel fuel during the compression stroke. In this study, the effects of six different input parameters on the performance and emissions of the natural gas/diesel fueled RCCI engine are studied using fractional factorial design (FFD) method, which is one of the design of experiment (DOE) methods. In this method, the effects of the interactions of input parameters, referred to as “factors,” on the outputs, referred to as “responses,” are investigated. The factors include premixed ratio (PR), start of first injection (SOI1), spray angle (SA), exhaust gas recirculation (EGR), start of second injection (SOI2), and mass fraction of first injection. Sixteen runs were conducted to evaluate the effects of the interaction between input factors on performance and emissions of a RCCI engine using a validated computational fluid dynamics (CFD) model. DOE results indicate that in order to increase gross indicated efficiency (GIE), higher premixed ratio, 85%, with wider spray angle, 150°, is an effective way. Meanwhile, carbon monoxide (CO) and unburned hydrocarbons (UHC) emissions as well as ringing intensity (RI) are decreased at this condition. To reduce NOx emissions, it is beneficial to raise premixed ratio from 55% to 85% or to use 40% EGR, independently.

Impact of secondary fuel injector in various distance on direct injection diesel engine using acetylene-bio diesel in reactivity controlled compression ignition mode

ABSTRACT Many researchers utilized acetylene fuel in conventional diesel engine in dual fuel mode. Dual fuel Reactivity Controlled Compression Ignition (RCCI) engine is established by modifying the Conventional Diesel Engine (CDE) intake manifold that supplies secondary fuel through the injector. The aim of the study is to analyze the acetylene-bio diesel fueled RCCI engine by varying the secondary fuel injector position in the intake manifold. The experiment was carried out by acetylene gas as a Low Reactivity Fuel (LRF) which is supplied by an injector at a distance of 243.5 mm, 288.5 mm, and 333.5 mm from the intake valve with a constant flow rate of 4 l/min during the suction stroke. The High Reactivity Fuel (HRF) B20 MOME (Mahua Oil Methyl Ester) is supplied through the injector at end of the compression stroke. The modified engine was tested for its performance, combustion, and emission characteristics. The result shows that the Brake Thermal Efficiency (BTE) at a distance of 243.5 mm from the intake valve increases all loads and achieves a brake thermal efficiency improvement of 2.27% from the B20 MOME fueled engine. The Exhaust Gas Temperature (EGT) and NOx, which are predominantly higher in biodiesel fueled engine, are reduced about 13.5% and 13.6% respectively at a distance of 243.5 mm from the intake valve in the RCCI mode combustion.

A comprehensive parametric, energy and exergy analysis for oxygenated biofuels based dual-fuel combustion in an automotive light duty diesel engine

Presently methanol based dual fuel reactivity controlled compression ignition (DFRCCI) has more and more attention in fuel and engine research field because of its potential in reducing the engine-out harmful emissions and evading the dependency on fossil fuel resources. However, while using methanol along with diesel in DFRCCI combustion, a substantial increase in incomplete combustion loss was observed at lower loads due to lower fuel stratification, global reactivity and in-cylinder temperature. Hence, to address this limitation, diesel fuel was replaced by a biodiesel, and a detailed experimental study was performed with energy and exergy analysis to show the potential of biodiesel over diesel. In this study, a modified automotive diesel engine was tested under CDC and DFRCCI combustion strategy using Methanol/ Diesel (M/D) and Methanol/ Biodiesel (M/BD) fuel combinations at 2100 rpm, 3.4 bar BMEP load condition. The experimental parametric study shows that 60% of methanol energy can be effectively utilised with an advanced direct injection and a moderate level of exhaust gas recirculation. Energy analysis clearly indicated the reason for the improvement in brake thermal efficiency in DFRCCI combustion. Reduced energy loss in the exhaust and coolant, increased brake thermal efficiency was observed in DFRCCI compared to CDC. However, increased incomplete combustion loss was observed in M/D DFRCCI combustion compared to CDC. Whereas, reduced incomplete combustion loss was observed while using biodiesel instead of diesel due to increased fuel stratification caused by the physical properties of biodiesel and in-cylinder temperature. Further, lower exergy destruction was observed in M/BD DFRCCI compared to M/D DFRCCI combustion.

Experimental Assessment of Effects of n-Butanol on Performance, Emission, and Combustion Characteristics of Mahua Oil Fueled Reactivity Controlled Compression Ignition (RCCI) Engine

The emission and combustion characteristics of diesel engine operated under reactivity controlled compression ignition (RCCI) mode are investigated in this study. A separate electronic fuel injector was mounted on the intake manifold of the engine meant for RCCI operation. RCCI mode of operation was conducted by injecting “n-butanol” as low reactivity fuel into the intake, and “mahua oil” as high reactivity fuel directly into the combustion chamber. Experimental results reported that smoke and nitric oxide (NO) emissions are significantly reduced by 45.4% and 33.1% through RCCI mode when compared with single fuel mode (mahua oil) at peak load. Carbon monoxide (CO) and unburnt hydrocarbon (HC) emissions were substantially increased at part load conditions in RCCI mode by increasing n-butanol energy share, while both HC and CO emissions were reduced at maximum power output. About 6.2% increase in brake thermal efficiency (BTE) of the engine was found when operated in RCCI mode, with up to 20% of n-butanol share; beyond this energy share, a marginal drop in BTE was noted at peak load. A substantial rise in cylinder pressure and heat release rate (HRR) was found while operating in RCCI mode. At part load, ignition delay was found to be longer in RCCI operation, but at supreme load condition, it was reduced. It was concluded that RCCI mode of operation improved the engine’s performance and similarly reduced smoke and NO emissions.

Mitigation of high pressure rise rate by varying IVC timing and EGR rate in an RCCI engine with high premixed fuel ratio

In a reactivity controlled compression ignition (RCCI) engine, when the ratio of premixed low-reactively fuel is high, unacceptable high pressure rise rate (PRR) always occurs. The objective of this study is to find effective ways of mitigating the high PRR in and biodiesel and gasoline fueled RCCI engine. Coupled KIVA4-CHEMKIN code was used to mimic the combustion process of RCCI engine with 70% of premixed gasoline. At first, parametric studies were conducted to investigate the effects of intake valve close (IVC) timing and exhaust gas recirculation (EGR) rate, respectively. Results indicate that delaying IVC timing and increasing EGR rate could mitigate the maximum PRR. Then, a two-stage optimization was undertaken by considering IVC timing and EGR rate at one time. To guide the optimization, contour maps on indicated mean effective pressure (IMEP) and emissions were generated. It was found that high EGR rate with advanced IVC timing would lead to satisfying results. Finally, two optimal cases were identified. Comparing with the cases of varying IVC timing and EGR rate individually, while resulting same acceptable maximum PRR, the optimal cases emit much lower NO, soot and CO emissions, and achieve slightly higher thermal efficiency.

Statistical and experimental investigation of single fuel reactivity controlled compression ignition combustion on a non-road diesel engine

In the present work, an attempt is made to implement the single fuel RCCI combustion on a non-road diesel engine using oxygenated renewable non-fossil fuel. In this study, isobutanol (high octane fuel − low reactivity fuel)/isobutanol-polyoxymethylene dimethyl ether blend (medium Cetane fuel − medium reactivity fuel) based reactivity controlled compression ignition combustion has been investigated on a modified single cylinder non-road diesel engine to control its engine out emissions and to improve the brake thermal efficiency. Various operating parameters have been optimized for a wide range of engine loads (i.e. from 1.3 bar BMEP to 3.9 bar BMEP) using response surface methodology and statistical significance of the used models have been recognized by analysis of variance. Then, numerical optimization has been performed using the desirability approach of response surface methodology. The predicted solutions are validated by engine experiments. Design of experiments approach saved many experimental trials and helped in understanding the effects of various operating parameters such as PODE energy ratio, the start of injection of a pilot and main fuel, fuel injection pressure of medium reactivity fuel, pilot injection mass, intake air temperature, and EGR on combustion, performance and emission characteristics. The predicted and actual experimental results show that a maximum 97% reduction in soot emission and 83% reduction in NO emission was achieved in single fuel RCCI combustion compared to conventional diesel combustion along with a 10.4% percentage increase in brake thermal efficiency.

Experimental investigation of iso-butanol/diesel reactivity controlled compression ignition combustion in a non-road diesel engine

As non-road engine emission control programs are developed largely in number of countries around the world, adopting a high efficiency and low emission combustion techniques has become essential. Flexible fuel operation using in-cylinder blending technique is a primary option for using higher octane fuel in a non-road diesel engine to mitigate emissions and fossil fuel dependency. In the present study, iso-butanol/diesel dual fuel reactivity controlled compression ignition concept is preferred considering the benefits of iso-butanol over other alcohol fuels and better combustion control over other low temperature combustion concepts. An experimental investigation is performed on a suitably modified single cylinder non-road diesel engine for the entire load range (0–100% engine full load) focusing on the effect of operating parameters (iso-butanol mass fraction, diesel injection timing, diesel injection pressure, diesel mass in split injection, and intake air temperature) on the dual fuel combustion, performance and emission characteristics. The reactivity controlled compression ignition combustion is analyzed at each load condition and the best operating points are selected based on brake thermal efficiency and emissions. The results indicated that increase in iso-butanol mass fraction with advanced start of injection of direct injected diesel fuel showed a 99% reduction in oxides of nitrogen and a 91% reduction in smoke emissions with 4.5% increase in brake thermal efficiency. Further the drawback in dual fuel combustion, hydrocarbon emission is reduced by 65% with an increase of intake air temperature from 303 K to 338 K. Also, both hydrocarbon and carbon monoxide emissions are reduced with increase in diesel injection pressure and mass of diesel fuel injected in first injection due to the enhanced mixture formation.

Numerical study on double injection techniques in a gasoline and biodiesel fueled RCCI (reactivity controlled compression ignition) engine

In an RCCI (reactivity controlled compression ignition) engine, the double injection strategy is a technical tool to control its combustion process. In this study, the effects of two key injection parameters, namely dwell and split fraction, are numerically investigated in a gasoline and biodiesel fueled RCCI engine. In the engine, gasoline is used as the premixed fuel; meanwhile, biodiesel is directly injected into the air-fuel mixture. The coupled KIVA4-CHEMKIN code was used to simulate the in-cylinder combustion process and the emissions formation. The gasoline/biodiesel reaction mechanism, which consists of 107 species and 425 reactions, was implemented in the code for detailed chemistry calculation. During the simulation, the dwells between 1st and 2nd SOI (start of injection) timings were varied at 5, 15, 25 and 35°CA, while the 1st SOI timing was fixed at −35 °C ATDC. Besides, the 1st pulse fractions were changed at 30%, 50% and 70%; accordingly, the rest of the biodiesel was injected through the 2nd pulse. The combustion characteristics (including in-cylinder pressure, HRR (heat release rate), ignition delay, PPRR (peak pressure rise rate) and combustion duration), engine performance and emissions (NO and soot) formations were compared under various operating conditions. The results show that double injection strategy results in longer ignition delay. In contrast with the dwells of 15° and 25°CA, the cases with dwells of 5° and 35°CA could result in acceptable PPRR, longer combustion duration, but slightly lower IMEP (indicated mean effective pressure). However, short dwell of 5°CA displays better results on NO and soot emissions. The combustion process with long dwell of 35°CA is both reactivity and mixing controlled.

Effects of reformed fuel composition in “single” fuel reactivity controlled compression ignition combustion

The present effort uses a combination of engine experiments and constant volume ignition delay calculations to investigate reformed fuel RCCI combustion. NOx emissions and efficiency are found to be a strong function of the engine operating parameters and soot emissions decrease with increasing fuel reforming due to a reduction in the mixing requirements of the diesel fuel. The impact of reformer composition is investigated by varying the syngas composition from 10% H2 to approximately 80% H2. The results of the investigation show that reformed fuel RCCI combustion is possible over a wide range of H2/CO ratios. Replacing CO with H2 resulted in a more reactive charge, decreased the combustion duration, and suppressed low temperature heat release. The suppression of low temperature heat release was explained through consumption of hydroxyl radicals by H2.

Dilution Sensitivity of Particulate Matter Emissions From Reactivity-Controlled Compression Ignition Combustion

Dual-fuel reactivity-controlled compression ignition (RCCI) combustion can yield high thermal efficiency and simultaneously low NOx and soot emissions. Although soot emissions from RCCI are very low, hydrocarbon (HC) emissions are high, potentially resulting in higher than desired total particulate matter (PM) mass and number caused by semivolatile species converting the particle phase upon primary dilution in the exhaust plume. Such high organic fraction PM is known to be highly sensitive to dilution conditions used when collecting samples on a filter or when measuring particle number using particle sizing instruments. In this study, PM emissions from a modified single-cylinder diesel engine operating in RCCI and conventional diesel combustion (CDC) modes were investigated under controlled dilution conditions. To investigate the effect of the fumigated fuel on the PM emissions, 150 proof hydrous ethanol and gasoline were used as low reactivity fuels. The data reveal that PM from RCCI combustion is more sensitive to the variation of dilution conditions than PM from single fuel conventional diesel combustion. RCCI PM primarily consisted of semivolatile organic compounds and a smaller amount of solid carbonaceous particles. The fumigated fuel had a significant effect on PM emissions' characteristics for RCCI combustion. Hydrous ethanol fueled RCCI PM contained a larger fraction of volatile materials and was more sensitive to the variation of dilution conditions compared to the gasoline fueled RCCI mode.

Experimental investigations of effects of hydrogen blended CNG on performance, combustion and emissions characteristics of a biodiesel fueled reactivity controlled compression ignition engine (RCCI)

The effects of hydrogen blended compressed natural gas (HCNG) on performance, combustion and emissions characteristics of biodiesel fueled compression ignition engine under reactivity controlled compression ignition (RCCI) mode were studied. The pongamia pinnata biodiesel (B100) as pilot fuel was directly injected into the engine cylinder during compression stroke whereas compressed natural gas (CNG) and 18% HCNG as main fuels were injected during suction stroke using electronic controlled unit. The experimental tests were conducted on the engine at constant speed of 1500 rpm with 5 kW electrical power output. The experimental results indicate brake thermal efficiency of the engine improved significantly up to 64% of HCNG energy share. HC, CO and smoke emissions at all HCNG energy shares are less as compared to base CNG. However, NOx emission increased marginally with HCNG but it is still less than base biodiesel. A notable point emerged from this study is that CO and HC emissions, which are major problems with CNG dual fuel engine, could be reduced significantly with HCNG and B100.

Experimental investigations of effects of EGR on performance and emissions characteristics of CNG fueled reactivity controlled compression ignition (RCCI) engine

Experimentaltests were carried out on a single cylinder diesel engine (7.4kW rated power at 1500rpm) under dual fuel mode (CNG-Diesel) with EGR (exhaust gas recirculation). Less reacting fuel (CNG) was injected inside the intake manifold using timed manifold gas injection system whereas high reactive diesel fuel was directly injected into the engine’s cylinder for initiation of ignition. EGR at different percentages (8%, 15% and 30%) was inducted to the engine through intake manifold and tests were conducted at alternator power output of 2kW and 5kW. The engine can operate under dual fuel mode with maximum CNG energy share of 85% and 92% at 5kW and 2kW respectively. The brake thermal efficiency of diesel engine improved marginally at 5kW power output under conventional dual fuel mode with the CNG share up to 37% whereas the efficiency did not change with up to 15% EGR however it decreased beyond the EGR percentage. NOx emission in diesel engine under conventional dual fuel mode decreased significantly and it further decreased drastically with EGR. The notable point emerged from this study is that CO and HC emissions, which are major problems at part load in reactivity controlled compression ignition engine (RCCI), decreased with 8% EGR along with further reduction of NOx. However, smoke emission is marginally higher with EGR than without EGR but it is still less than conventional mode (Diesel alone). The new concept emerged from this study is that CO and HC emissions of RCCI engine at part load can be reduced using EGR.

Application of Dynamic ϕ–T Map: Analysis on a Natural Gas/Diesel Fueled RCCI Engine

In this study, dynamic ϕ–T map analysis was applied to a reactivity controlled compression ignition (RCCI) engine fueled with natural gas (NG) and diesel. The combustion process of the engine was simulated by coupled kiva4-chemkin with a diesel oil surrogate (DOS) chemical mechanism. The ϕ–T maps were constructed by the mole fractions of soot and NO obtained from senkin and ϕ–T conditions from engine simulations. Five parameters, namely, NG fraction, first start of injection (SOI) timing, second SOI timing, second injection duration, and exhaust gas recirculation (EGR) rate, were varied in certain ranges individually, and the ϕ–T maps were compared and analyzed under various conditions. The results revealed how the five parameters would shift the ϕ–T conditions and influence the soot–NO contour. Among the factors, EGR rate could limit the highest temperature due to its dilute effect, hence maintaining RCCI combustion within low-temperature combustion (LTC) region. The second significant parameter is the premixed NG fraction. It could set the lowest temperature; moreover, the tendency of soot formation can be mitigated due to the lessened fuel impingement and the absence of C–C bond. Finally, the region of RCCI combustion was added to the commonly known ϕ–T map diagram.

Effects of fuel ratio and injection timing on gasoline/biodiesel fueled RCCI engine: A modeling study

RCCI (reactivity controlled compression ignition) has drawn much attention since it was proposed, as it could lead to high performance and clean combustion. The original concept of an RCCI engine is to use gasoline and diesel as the low and high reactivity fuels, respectively. In this study, biodiesel is considered as a substitute of diesel. Hence, research was numerically conducted on a gasoline/biodiesel fueled RCCI engine. To simulate the combustion process, coupled KIVA4–CHEMKIN was used. The gasoline/biodiesel reaction mechanism as implemented in the code was developed by the authors. Two major factors, namely gasoline to total input energy ratio and SOI (start of injection) timing, have been considered. The varied gasoline energy ratios were applied to both C-SOI (conventional SOI) and A-SOI (advanced SOI) timings. Comparing the combustion characteristics between two SOI timings with varied gasoline energy ratios, it is found that A-SOI could offer more controllability on start of combustion, combustion phasing etc. when varying gasoline ratio. As for the emissions formation, increases in gasoline could reduce NOx and soot emissions simultaneously by achieving more homogeneous combustion. However, the designed spray angle of 78° for C-SOI, when used with A-SOI, would increase the soot formation especially when more biodiesel is injected.

Investigation of the Combustion Instability-NOx Tradeoff in a Dual Fuel Reactivity Controlled Compression Ignition (RCCI) Engine

Investigation of the Combustion Instability-NOx Tradeoff in a Dual Fuel Reactivity Controlled Compression Ignition (RCCI) Engine